Stackable chair



FIG. 1 is a front, top perspective view of a stackable chair showing my new design;

FIG. 2 is a side perspective view thereof;

FIG. 3 is a side elevation view thereof;

FIG. 4 is a front elevation view thereof;

FIG. 5 is a rear elevation view thereof; and,

FIG. 6 is a top plan view thereof. 

CLAIM The ornamental design for a stackable chair, as shown and described. 